Alcoholysis of glycerides



Patented Oct. 24, 1939 y I V UNITED srnres Parser or ies ALCOHOLYSIS OF GLYCERIDES Virgil L. Hansley, Niagara Falls, N. Y assignor to E. I. du Pont 'de'Nemours & Company, Wilmington, Del, a corporation of Delaware No Drawing. Application September 21, 1936, Serial No. 101,790

22 Claims. (Cl. 260-410) This invention relates to the preparation of excess of the alcoholizing alcohol, a hydrogenaesters and more particularly to a non-catalytic tion catalyst and subjecting the mixture under method of converting fatty acid glycerides to hydrogen pressure to a temperature suitable for fatty acid esters ofmonohydric aliphatic alcohols. efiecting a olys s an hy ti Alcoholysis reactions involving fatty acid glyc- I have discovered that a reaction temperature erides are commonly effected by heating the glyc- 0f apprc ima y 175C is sufficiently h to eride with a large excess of an aliphatic alcohol efiect the alcoholysis of a fatty acid glyceride. in the presence of hydrochloric acid as catalyst. At a temperature of 150 C. the alcoholysis reac- While this method may be used to produce good tion pr c at n ppre i le r e, which howyields of fatty acid esters of monohydric ali- 'ever,'is too slow to be of practical value. But, 10

phatic alcohols by heating the reaction mixture at 175 C. or at higher temperatures, the reacfor a long period of time at the refluxing tem- ,tion is rapid and satisfactory conversions may be perature, nevertheless, it has several disadvanrealized within a reasonable time in the presence tages when used inlarge scale commercial operaof an excess of alcohol. Relatively high tempertions. Aside from the extremely long reaction atures may be emp o to i c ease the rate of 15 time that is necessary to effect good yields of reaction providing such temperatures do not product by this method, the hydrochloric acid cause appreciable decomposition of the fatty acid catalyst requires the use of relatively expensive glyceride or the ester product. In general, I precorrosion resistant equipment. In addition, the fer to practice my invention at a temperature of hydrochloric acid is slowly converted by reaction about 200-225" C. although any temperature 0 with the alcohol present to the corresponding Within the range of l75-300 C. may be employed alkyl chloride, for example, to methyl chloride with good res lts W th ost fatty acid y d when methanol is used. This is not only waste- Since the alcoholysis reactions under considful and costly but causes a gradual and effective eration are equil r um a ons, it S necessary lowering of' the concentration of the catalyst in to use an excess of the alcohol in order that good the reaction mixture as the reaction proceeds. conversions of the glyceride to the simple esters Furthermore, hydrochloric acid is not entirely may be realized, When esters of the lower alisuitable as a catalyst for such reactions since phatic alcohols are desired, I have found that 0.75

strong acids induce decomposition and polymerto 2.0 parts by weight of the alcohol to 1 part ization reactions when the glyceride involved in by weight of the glyceride provides a suitable ex- 30 the reaction is highly unsaturated. cess of the alcohol. Although excellent yields of An object of the present invention is to prothe simple esters may be obtained by using more vide an improved method for producing fatty acid than about 2 parts of alcohol, such a large excess esters of monohydric aliphatic alcohols from is generally undesirable in that subsequent opfatty acid glycerides in general. Another object eratiohs involving the distillation and recovery of 35 is to provide a method for producing such esters the excess alcohol then become excessively exin improved yields without the use of a catalyst. pensive. When less than about 0.75 parts by A further object is a method for simultaneously weight of alcohol to 1 part of glyceride is emalcoholizing and hydrogenating unsaturated fatployed, conversions of the glyceride to the simple ty acid glycerides to produce saturated fatty acid ester are relatively low and the process becomes esters of monohydric aliphatic alcohols. Other impractical for commercial use.

O j Will b hereinafter apparent. To practice my invention, I may mix the glyc- These objects are accomplished in accordance eride with a suitable excess of the alcohol and with the present invention by reacting a fatty heat the mixture to a temperature above about acid glyceride with a monohydric aliphatic alco- 175 C., e. g. at 200-225 C. under pressure. A 5

hol under Pressure, in absence of an QJ convenient method of attaining asuitable presholysis catalyst at a temperature sufliciently high sure for the reaction comprises heating the reto effect the alcoholysis reaction but not high action mixture in an autoclave. enough to cause substantial decomposition of the The important factors in the successful prac- 50. fatty acid glyceride or the product ester of the tice of my process are, as noted above, the tem- 5 monohydric aliphatic alcohol. If the fatty acid perature of operation and the concentration of glyceride is unsaturated and a saturated ester of the reactant alcohol in the reaction mixture. In

W monohydric aliphatic alcohol is desired, the order that the concentration of the reactant alcoglyceride may be alcoholized and hydrogenated hol-is not excessively lowered during operation 65 simultaneously by emp oving, in addition to an of the process at a suitable temperature, it is necessary that the reaction be carried out under pressure. The required pressure may be conveniently attained by heating a suitable reaction mixture in an autoclave within the temperature range of 1'75-300 C. If desired, and provided a suflicient excess of reactant alcohol is employed, vapors may be periodically bled off from the autoclave, although'I have found that excellent results may be obtained without, bleeding. My

process may be operated at any pressure corresponding to the vapor pressure of the reaction mixture at temperatures within the limits of PIS-300 C. The pressure for a given temperature of operation within the above range will vary somewhat with the reactants employed and also with the proportion of the reactants and reaction products in the reaction mixture.

My process is particularly well suited for use with the lower monohydric aliphatic alcohols such as methyl, ethyl, propyl, butyl and amyl alcohols,

and isomers of the latter three alcohols. Whenany of these alcohols are used, they may be employed in quantities as specified in the previous paragraph. My process also may be practiced employing monohydric aliphatic alcohols containing more than 6 carbon atoms per molecule with good results, provided a larger excess of the alcohol is employed. Although my process is suitable for the preparation of fatty acid esters of monohydric alcohols generally; I have found it to be especially well adapted to the preparation of the methyl and ethyl esters of fatty acids. These esters may be produced in excellent yields in accordance with my invention and may be conveniently separated from the reaction mix ture without excessive decomposition by distillation under reduced pressure.

I prefer to employ alcohol in an anhydrous state as one of the reactants in my process. However, small quantities of water may be present without appreciably lowering the conversion to simple esters. When an appreciable quantity of wvater is present in the reaction mixture, hydrolysis of the glyceride or the ester reaction product becomes appreciable, thus lowering the yield of ester.

The present invention may be employed adv'antageously to convert either saturated or highly unsaturated glycerides to the corresponding saturated or unsaturated simple esters; I have found that there is no great tendency for decomposition and polymerization reactions to occur in my process, provided the reaction temperature does not exceed approximately 300 C. In general, improved yields, which in some cases are practically quantitative, of simple esters are obtainable from fatty acid glycerides in accordance with the prestaneously it is only necessary that a hydrogenation catalyst be present in the above described ent invention.

I have further discovered that an unsaturated.

fatty acid glyceride may be simultaneously alcoholized and hydrogenated to produce saturated simple esters of fatty acids. In order foralcoholysis and hydrogenation to be effected simulmixture of unsaturated glyceride and monohydric aliphatic alcohol and that the mixture be subjected to a hydrogen pressure of about 500 lbs/sq. in. or greater during the alcoholysis. In general, a hydrogen pressure of 500 to 1000 lbs/sq. in. is entirely satisfactory'although higher pressures may be employed with good results. Any efficient hydrogenation catalyst may be employed. I have found the ordinary nickel catalyst, supported on kieselguhr, to be entirely satisfacgive a total pressure of 1000 lbs/sq. in. After 10 376 gms. or 68.1% of a mixture of methyl esters,

of the acid constituents of the coconut oil, boiltory. The concentration of hydrogenation catalyst required is the same as that normally em.- ployed in hydrogenation of glycerides and similar material. I have found that temperatures suitable for effecting alcoholysis alone are also suit- 5 able for effecting the combined alcoholysis and hydrogenation.

The following examples illustrate but do not limit my invention:

Example I 10 Palm oil, 1 kg., was heated in an autoclave with 1 kg. of methanol to 200 C. for 10 hours. The reaction mixture was cooled and washed with water to remove the by-product glyceroland excess methanol. The methyl estersobtained, boiling at 190213 C. at 15 mm. pressure, corresponded to a 93.5% conversion. The iodine number ,of the original oil was 50.9 whereas that of the product was 48.7.

Example II Palm oil, 1 kg., was heated as in Example I, to 200 C. with an equal weight of methanol, but in addition, 50 gms. of a supported (on kieselguhr) nickel catalyst was incorporated into the charge. During the heating the mixture was subjected to a hydrogen pressure sufficient to hours of reaction time the mixture was cooled, so

filtered to remove the catalyst, and washed with water. The yield of methyl ester mixture obtained, boiling at 190-213 C. at 15 mm. pressure, was 98.0% of the theoretical. The i'odine number of the originaloil was 50.9 and of the product 9.9.

Example III Castor oil (Bakers #3 grade), 535 gms., together with 1000 cc. of methanol and 25 gms. of supported nickel catalyst were placed in an autoclave and subjected to hydrogen pressure suflicient to give a total pressure of 1000 lbs/sq. in. at a temperature of 200 C. After 14 to 16 hours under these conditions methyl hydroxy stearate in an amount equivalent to an 88.3% conversion was isolated. The iodine numberv of the product (Wijs) was 3.1 and the saponification number was 178.

Example IV Chinawood oil, 552 gms., was heated in an auto-- clave with 1000 cc. of methanol at 175 C. for 16 hours. After washing, the reactionproduct was distilled at a pressure of 2 mm,. A yield of boiling at -190 C. was obtained. The saponification number of the product was 193 and its content of free acid, calculated as oleic acid, was

' Example V equivalent to 0.45%. n

Example VI Menhaden oil, 500 gms. heated with 500 gms. of methanol at 300 C. for 5.5 hrs. yielded, upon vacuum distillation, methyl esters equivalent to a 79% conversion. 18.4% of the original oil remained unconverted.

The above examples illustrate but a ew of the many preparations for which the present invention may be employed. Various modifications of the process illustrated by the above examples may be utilized without departing from the scope of the present invention.

The present process for the alcoholysis of glycerides to produce fatty acid glycerides of monohydric aliphatic alcohols is well adapted for operation in a continuous manner. For example, a fatty acid glyceride and a suitable excess of an alcohol may be forced through a reaction chamher under pressure and at a temperature suitable for effecting the alcoholysis in the reaction chamher, and the reaction products and excess alcohol separated upon discharge from the reaction chamber. In such a continuous operation I prefer to employ temperatures in the neighborhood of 225-300 C. in order that the reaction may be rapidly effected, although temperatures as low as 175 C. may be employed if the rate of passage of the reaction mixture through the reaction chamber is sufliciently slow. The rate of passage of the reaction mixture through the reaction chamber may be regulated so that a substantial amount of conversion is effected before the mixture is discharged from the chamber. If relatively high temperatures are employed such as temperatures of 225-300 C. the rate of passage through the chamber may be appreciably greater than the rate required when lower temperatures are employed in order to produce the same degree of conversion.

I claim:

1. The process comprising reacting a fatty acid glyceride and a monohydric aliphatic alcohol in the absence of an alcoholysis catalyst at a temperature of not less than 175 C. and under a pressure corresponding to said temperature in a closed system, to produce a fatty acid ester of said alcohol.

2. The process comprising reacting a fatty acid glyceride and a monohydric aliphatic alcohol in the absence of an alcoholysis catalyst at a temperature of about 175 to 300 C. and under a pressure corresponding to said temperature in a closed system, to .produce a fatty acid ester of said alcohol.

3. The process comprising reacting a fatty acid glyceride and a monohydric aliphatic alcohol in the absence of an alcoholysis catalyst at a temperature of about 200 to 225 C. and under a pressure corresponding to said temperature in a closed system, to produce a fatty acid ester of said alcohol.

4. The process comprising reacting a fatty acid glyceride and a monohydric aliphatic alcohol 'in the absence of an alcoholysis catalyst in a weight ratio of 1 part glyceride to about 0.75. to 2 parts alcohol at a temperature of not less than 175 C. and under a pressure corresponding to said temperature in a closed system, to produce a fatty acid ester of said alcohol.

5. The process comprising reacting a fatty acid glyceride and a monohydric aliphatic alcohol in the absence of an alcoholysis catalyst in a weight ratio of 1 part glyceride to about 0.75 to 2 parts algohol at a temperature of 175 to 300 C; and

under a pressure corresponding to said temperature in'a closed system, to produce a fatty acid ester of said alcohol.

6. The process comprising reacting afatty acid glyceride and a monohydric aliphatic alcohol in the absence of an alcoholysis catalyst in a weight ratio of 1 part glyceride to about 0.75 to 2 parts alcohol at a temperature of about 200 to 225 C. and under a pressure corresponding to said temperature in a closed system, to produce a fatty acid ester of said alcohol.

7. The process comprising subjecting a mixture comprising a fatty acid glyceride and a monohydric aliphatic alcohol containing less than 6 carbon atoms per molecule in a weight ratio of 1 part of glyceride to about 0.75 to 2 parts of alcohol to a temperature of about 175-300 C. in the absence of an alcoholysis catalyst and under a pressure corresponding to said temperature in a closed system, for a sufficient time to effect conversion of said glyceride to a fatty acid ester'of said alcohol.

8. The process comprising subjecting a mixturecomprising a fatty acid glyceride and a monohydric aliphatic alcohol containing less than 6 carbon atoms per molecule in a weight ratio of 1 part of glyceride to about 0.75 to 2 parts of alcohol to a temperature of about 200-225 C. in the absence of an alcoholysis catalyst and at a pressure corresponding to said temperature in a closed system, for a sufficient time to effect conversion of said glyceride to a fatty acid ester of said alcohol.

9. The process comprising subjecting a mixture comprising a fatty acid glyceride and methanol in a weight ratio of 1 part glyceride to about 1 part methanol in a closed system to heat at a temperature of about 175 to 300 C. in the absence of an alcoholysis catalyst and under a corresponding pressure to produce a fatty acid ester of methanol.

10. The process comprising subjecting a mixturecomprising a fatty acid glyceride and meth anol in a weight ratio of 1 part glyceride to about 1 part methanol in a ,closed system to heat at a temperature of about 200 to 225 C. in the absence of an alcoholysis catalyst and under a corresponding pressure to produce a fatty acid ester of methanol.

11. The processcomprising subjecting a mixture comprising a fatty acid glyceride and ethanol in a weight ratio of 1 part of glyceride to about 1 part of ethanol in a closed system to heat at a temperature of about 175 to 300 C. in the absence of an alcoholysis catalyst and under a corresponding pressure to produce a fatty acid ester of ethanol.

12. The process comprising subjecting a mixture comprising a fatty acid glyceride and ethanol in a weight ratio of 1 part of glyceride to about 1 part of ethanol in a closed system to heat at a temperature of about 200 to 225 C. in the absence of an alcoholysis catalyst and under a corresponding pressure to produce a fatty acid ester of ethanol.

13. The process for producing a methyl ester of a fatty acid comprising continuously forcing a fatty acid glyceride and methanol together while maintaining a weight ratio of 1 part of said glyceride to about 0.75 to 2 parts of said methanol through a reaction chamber maintained at a temsponding to said temperature in a closed system,

at such a ratevthat a substantial conversion of 3| said glyc'eride to said ester is efiected and sens-,

rating the reaction products and excess methanol discharged from said reaction chamber. M 14. The process for producing a methyl ester of a fatty acid comprising continuously forcing 15. The process for producing an ethyl ester of:

a fattyacid comprising continuously forcing a fatty acid glyceride and ethanol together while maintaining a weight ratio of 1 part of said glyceride to about 0.75 to 2 parts of said ethanol through a reaction chamber maintained at-' a temperature of 175 to 300 C. in the absence of an alcoholysis catalyst under a pressure corresponding to said temperature in a closed system, at such a rate that a substantial conversion of said glyceride to said ester is effected and separating the reaction productsand excess ethanol discharged from said reaction chamber..

16. The process for producing an ethyl ester of a fatty acid comprising continuously forcing a fatty acid glyceride and ethanol together while maintaining a weight ratio of 1 part of said glyceride to about 0.75 to 2 parts of said ethanol through a reaction chambenmaintained ata temperature of 225 to 300 C. in theabsence of an alcoholysis catalyst under a pressure corresponding to said temperature in a closed system,'

at such a rate that a substantial conversion of. said glyceride to said ester is efiected and separating the reaction products'and excess ethanol discharged from said reaction chamber.

17. The process for preparing a saturated fatty acid ester of a-monohydric aliphatic alcohol con- ,taining less than 6 carbon atoms per molecule which'comprises subjecting a mixture comprising an unsaturated, fatty acid glyceride and said alcohol in a weight ratio of 1 part of glyceride to about 0.75 to 2 parts of alcohol in the presence of a hydrogenation catalyst to a hydrogen pressure of. not -less than ab0ut'500 lbs. per sq. in. at a -temperature of to 300 C., in the absenceof an alcoholysis catalyst.

18. The process for preparing a saturated fatty acid ester of a rnonohydric aliphatic alcohol con-- taining less than 6 carbon atoms per molecule which comprises subjecting a'mlxture. comprising an unsaturated fatty acid glyceride and said alcohol in a weight ratio of 1 part of glyceride to about 0.75 to 2 parts of alcohol in thepresence oi a hydrogenation catalyst to a hydrogen pressure of about 500 to 1000 lbs/sq. in at atemperature of about 200 to225 C.,-in the absence of analcoholysis catalyst 19. The process for preparing a saturated fatty acid ester of methanol which comprises subject-' ing a mixture comprising an unsaturated fatty acid glyceride and methanol in a weight ratio of about 1:1 in the presence ofa nickel hydrogenation catalyst to a hydrogen pressure of about 500 to 1000,1bs./s q.in. at a temperature of 175 catalyst.

20. The process for preparing a saturated fatty acid ester of methanol which comprises subjecting a mixturecomprising an unsaturated fatty acid glyceride and methanol in a weight ratio of about 1:1 in the presence of a nickel hydrogenation catalyst to a hydrogen pressure of about 500 to'1000 lbs/sq. in. at a temperature of about 200 to 225 C., in the absence of an alcoholysis catalyst. A I

21. The process for preparing a saturated fatty acid ester of ethanol which comprises subjecting a mixture comprising an unsaturated fatty acid glyceride and ethanol in a weight ratio of about 1:1 in the presence of a nickel hydrogenation catalyst to a hydrogen pressure of about 500 to 1000 lbs/sq. in. at a temperature of 175 to 300 C., in the absence of an alcoholysis catalyst.

22. The process for preparing a saturated fatty acid ester of ethanol which comprises subject'- ing a mixture comprising an unsaturated fatty acid glyceride and ethanol in a weight ratio of about 1:1 in the presence of a nickel hydrogenation catalyst to a hydrogen pressure of. about 500 to 1000 lbs/sq. in. at a temperature of about 200 to 225 C., in the absence of an alcoholysis catalyst. I

' VIRGIL L. HANSLEY. 

